Tuhinga 27: 56–80 Copyright © Museum of New Zealand Te Papa Tongarewa (2016) A review of the distribution and size of prion (Pachyptila spp.) colonies throughout New Zealand Sarah E. Jamieson,*‡ Alan J.D. Tennyson,* Kerry-Jayne Wilson,** Elizabeth Crotty,* Colin M. Miskelly,* Graeme A. Taylor*** and Susan M. Waugh* *Museum of New Zealand Te Papa Tongarewa, PO Box 467, Wellington, New Zealand **West Coast Penguin Trust, PO Box 70, Charleston, West Coast, New Zealand ***Department of Conservation, PO Box 10420, Wellington, New Zealand ‡ Current address: Wildlife Research and Monitoring Section, Ministry of Natural Resources and Forestry, c/o Trent University, 2140 East Bank Drive, Peterborough, ON K9L 0G2, Canada ABSTRACT: Prions are among of the most numerous birds of the Southern Ocean, and yet their populations are poorly documented. New Zealand has breeding populations of four of the six recognised species, all with large population sizes. The remaining two species occur naturally in the New Zealand zone but do not breed there. This review reports data collated from the scientific literature, government archives and unpublished information about the population sizes of prions gathered since earliest scientific records in New Zealand (1773, during James Cook’s second voyage) until the present day. The study focuses on breeding populations, and reports data about population size and presence or absence of prion populations from sites throughout the New Zealand region. The summary presented provides a solid baseline for future population assessments and identifies priority sites where future surveys are warranted. KEYWORDS: prions, Pachyptila, population sizes, population distribution, Procellariiformes, range, seabirds, New Zealand. collect the baseline data necessary for robust evaluations of Introduction its population trends and conservation status. Seabirds are one of the most globally threatened groups of Many seabird species rely on remote islands for breeding birds (Croxall et al. 2012). They face a multitude of and nest in burrows, making the collection of even the most pressures, such as interactions with commercial fisheries, basic data challenging. Further, in New Zealand access to pollution, climate change, plastic ingestion and disturbances many of the southern nearshore islands is severely restricted on the breeding grounds, from both humans and invasive to anyone other than traditional owners or occupiers, and species (Carney & Sydeman 1999; Gregory 2009; Hilton & then often limited to the March–May muttonbirding season Cuthbert 2010; Anderson et al. 2011). For many seabird (Moller et al. 2009), a period that does not coincide with the species, adequate knowledge of their distribution is lacking breeding season of many seabird species, including prions. (Croxall et al. 2012). This paucity of the most basic of data Prions (Pachyptila spp.) are small petrels (120–200g inhibits the conservation of these species. Furthermore, a average weight; Miskelly 2013a,b), are nocturnal on poor understanding of a species’ range makes it difficult to land, and nest in burrows or crevices, mostly on remote Distribution and size of prion (Pachyptila spp.) colonies throughout New Zealand 57 predator-free islands. Globally, there are six species of prion, In this paper we collate data from a wide variety of sources all of which breed on islands in the Southern Ocean: broad- to describe the distribution of prions breeding within the billed prion (P.vittata), Salvin’s prion (P.salvini), Antarctic New Zealand region, and if the data were available, we prion (P.desolata), thin-billed prion (P.belcheri), fairy prion report information on population numbers and trends. (P. t u r t u r ) and fulmar prion (P.crassirostris). Although they From this information we make recommendations for are one of the most abundant groups of seabirds (up to monitoring prion populations with the aim of identifying 95 million individuals; Brooke 2004) and are all listed by colonies that cover the geographic range of each species, the International Union for Conservation of Nature as of but also those that are the most practical to monitor owing ‘Least Concern‘ (IUCN 2016), they still face significant to relative accessibility. Our priority list includes those sites population threats. that have already had some history of monitoring. We also recommend that the population size for each recorded First, prions are among the most common species of colony is estimated. As initial counts of all colonies are seabird to succumb to beach-wreck (e.g. Harper 1980; completed, other priority sites for long-term monitoring Post 2007; Powlesland 1989). For example, during a severe will become apparent. This review does not provide inform - weather event in July 2011, approximately 250,000 prions ation about the biology of prions, nor their distributions (approximately 200,000 of which were broad-billed prions) outside of New Zealand. While we have attempted to blew ashore and died along the west coast of New Zealand include both published and unpublished records to provide (Miskelly 2011a; Tennyson & Miskelly 2011). Climate- a comprehensive overview, it is inevitable that some change models forecast that such storms are likely to increase information will have been missed. in both frequency and intensity (Easterling et al. 2000; Alley et al. 2003). This could have significant detrimental effects on population numbers of prions. Second, prions are Methods surface-feeders that rely on planktonic crustaceans, molluscs A literature review was conducted using primary, secondary and fish. It has been predicted that over the next 90 years and unpublished sources (sources and methods are described there will be a 6.3% decline in ocean productivity (Yool et in Waugh et al. 2013). Raw data were also gleaned from the al. 2013). Much of this decline will be due to a significant authors’ personal field notebooks and those of other decrease in key nutrient levels in surface waters, resulting contributing researchers. We follow the taxonomy and in large-scale effects on the lower trophic levels. In turn, this nomenclature of Gill et al. (2010) and present the results in could resonate throughout the ecosystem (Yool et al. 2013) taxonomic order. and lead to diminished feeding opportunities for surface- We report records of birds on land only, omitting feeding birds. Monitoring even abundant species such as observations of birds on the water, in the air or reported as beach-wrecks. We assumed that the presence of birds ashore prions for assessing changes in marine ecosystems is thus signified breeding; however, birds found in skua middens clearly important; as apex predators, prions are sensitive may have been killed elsewhere (e.g. on the water) and trans- indicators of change throughout these systems. And third, ported to land. Depending on the information available in introduced mammalian predators have extirpated popu - the original source, we described records as individuals (when lations of small seabirds from many islands in New Zealand no information on breeding status was given), breeding pairs since scientific records began 250 years ago (Taylor 2000a). (when some indication of breeding was provided and we Accurate and detailed information about the distribution note the presence of eggs or chicks) or burrows (when we had and abundance of seabirds from the earliest days of scientific information only on the nesting structures themselves, with recording to today would enable these changes to be docu- no information on bird occupancy; note that most prion mented and their impact on species’ conservation status to be nests are in soil burrows, and while in some cases the birds assessed (Warham 1996). However, globally there is a lack of also nest in crevices, such nests are usually also reported as baseline data for most prion populations, with just a few burrows, as most authors did not distinguish between nest exceptions (e.g. Catry et al. 2003; Taylor 2011). The first types). If some level of systematic surveying was conducted, step in determining prion population trends is establishing then the sampling protocol was described as a ‘count‘, the distribution of the species, which is best done during the otherwise it was recorded as an ‘observation‘. A few breeding season, when they are ashore. individual records of live birds on islands well outside their 58 Tuhinga, Number 27 (2016) 50 Observations Counts 40 30 20 Number of records 10 0 Before 1900 1900s 1910s 1920s 1930s 1940s 1950s 1960s 1970s 1980s 1990s 2000s 2010s Fig.1 Temporal distribution of population records for prion (Pachyptila spp.) colonies within New Zealand. known breeding range (e.g. a broad-billed prion on Motunau 31 records for broad-billed, Antarctic, fairy and fulmar I., Canterbury (Cox et al. 1967) and an Antarctic prion prions, respectively. Prions were found on all major offshore on Houruakopara I., Chatham Is (Imber 1994)) were con- island groups except the Kermadec Is. There were no records sidered to be vagrants. Brief observations that did not add of Salvin’s or thin-billed prions breeding on New Zealand any significant data to more comprehensive observations islands. This was expected, as they are not known to breed were not listed (e.g. there are some records of a species being in the southwest Pacific Ocean (Marchant & Higgins 1990), present on an island when there are other records of actual but it is noted that thin-billed prions were recorded as population estimates from a similar time). possibly breeding at Macquarie I. (Brothers 1984). Fairy We used the names of localities as they are reported by prions had the most expansive New Zealand range, spanning Land Information New Zealand (Land Information New 1650km in distribution from north to south. Antarctic Zealand 2012; Harriss 2016). Island and islands are prions had the most restricted range; they were found almost abbreviated to ‘I.’ and ‘Is‘, respectively. In some cases, text exclusively at the Auckland Is. ‘Observations’ far out - in parentheses after the site name gives information to numbered ‘counts’ (251 versus 51; Fig.1).